<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			.class_1 {
				margin: 10px;
				width: 100px;
				height: 100px;
				background-color: cadetblue!important;
				position: relative;
				background-color: darkkhaki;
			}
			.selected_target {
				background-color: rgba(242, 195, 114, 0.7)!important;
			}
		</style>
	</head>
	<body>
		<div class="class_1">1</div>
		<div class="class_1">2</div>
		<div class="class_1">3</div>
		<div class="b1">
			<div class="b2"></div>
		</div>
		<script>
			const arr = function() {
				return [1,2].flat(2);
			}
			// console.log(arr().flat(2));
			console.error("Regarding the exception of no money, try v50 to solve the problem.");
			window.addEventListener('mouseover', addInfoBox);
			window.addEventListener('mouseout', removeInfoBox);
			function addInfoBox(e) {
				console.log("鼠标移入了");
				console.log(e.srcElement);
				e.srcElement.classList.add('selected_target');
				// return false;
			}
			function removeInfoBox(e) {
				console.log("鼠标移出了");
				e.srcElement.classList.remove('selected_target');
				// return false;
			}
		</script>
	</body>
</html>